**Core Concept**
Fusion of teeth, also known as dental fusion, is a rare congenital anomaly where two or more adjacent teeth fail to separate during dental development. This condition is characterized by the partial or complete union of two or more teeth, resulting in a single tooth structure with two or more distinct dental crowns.

**Why the Correct Answer is Right**
Fusion of teeth is more common in the primary dentition, particularly in the maxillary first molars. The exact etiology of dental fusion is unclear, but it is thought to be related to genetic and environmental factors that affect dental development. The process of tooth formation involves the coordinated interaction of multiple cell types and signaling pathways, and disruptions in these processes can lead to anomalies such as dental fusion.

**Why Each Wrong Option is Incorrect**
**Option A:** Premature birth is associated with various dental anomalies, but it is not a specific risk factor for dental fusion.
**Option B:** Dental impaction is a condition where a tooth fails to erupt into the oral cavity, but it is distinct from dental fusion.
**Option C:** Dental agenesis, or the absence of one or more teeth, is a different dental anomaly that is not related to dental fusion.

**Clinical Pearl / High-Yield Fact**
Dental fusion can be a challenge for dental and orthodontic treatment, as it can affect the overall alignment and function of the teeth. A thorough understanding of the etiology and characteristics of dental fusion is essential for accurate diagnosis and treatment planning.

**Correct Answer:** C.